Devices for producing manganese dioxide by electrolysis



R. DUFOUR ETAL 2,867,570

DEVICES FOR PRODUCING MANGANESE DIOXIDE BY ELECTROLYSIS Jan. 6, 1959 Filed Oct. 11, 1955 INVENTORS Rene fill/bur ATTORNEYS United States Patent s i it DEVICES FOR PRODUCING MANGANESE DIOXIDE BY ELECTROLYSIS Ren Dufour and Marcel Verron, Paris, and Alphonse Gabriel Le Magoarou, Colombes, France, assignors to Socit Anonyme Cartoucherie Francaise, Paris, France, a corporation of France Application October 11, 1955, Serial No. 539,902

Claims priority, application France October 14, 1954 13 Claims. (Cl. 204-83) The present invention has for its object an improved device by means of which manganese dioxide of higher quality may be manufactured by electrolysis at a reduced cost.

It is known that the electrolysis of a manganese salt between a cathode (made, e. g., of lead) and a lead anode in a galvanic battery results in a deposit of manganese comes acid in the anodic region and alkaline in the cathodic region.

The gelatinous deposit on the cathode is a poor conductor of electricity and, accordingly, creates an additional resistance to the flow of the current. To overcome such resistance, it is, therefore, necessary to increase the potential difference between the electrodes to an inadmissible extent.

Accordingly, it has already been proposed to remove the gelatinous deposit formed on the cathode by continuously stirring the bath in order to mix the acid anodic solution and the alkaline cathodic solution, thus preventing the cathodic region from becoming too alkaline. However, such stirring does not create the best operating conditions for the electrolysis, inasmuch as, in the course of the electrolysis process, the average acidity of the bath regularly increases, because manganese is being continuously withdrawn from the bath.

In order to mitigate the aforesaid drawback and to avoid thefo'rmation of an insulating layer on the cathode, it has been proposed to give a relatively considerable degree of acidity to the bath, so that, in the cathodic region, the pH remains in all points below the pH corresporiding to the precipitation of the manganous hydroxide. Most existing installations operate with such a relatively low pH. However, when operating in this well known manner, it is difiicult to adjust the pH of the different regions, and, particularly, to give it the necessary optimum value at the anode as well as at the cathode. As a matter of fact, it is difficult to correctly control the mixing process by stirring and convection.

Now, we have found that there are optimum values for the anodic bath as well as for the cathodic bath.

When operating with a well defined current density and at a temperature which also is Well defined, it is found that the aspect, and, particularly, the adherence, of the manganese dioxide deposited on the anode vary as the pH of the bath in that region. We have found that a very low acidityin the order of 2 to 3 gr. of H 80 per liter-produces a satisfactory adherence (that is to say, suflicient to prevent the dioxide from peeling oif from the anode and from spreading into the bath, while,

'ice

at the end of the operation, enabling a suitable removal of the dioxide deposited on the anode).

Similarly, there is an optimum value of acidity for the cathodic region. This is particularly true when the cathode comprises impure manganese dioxide (as is the case in some forms of our invention) which must be reduced to the form of manganous salt, on account of the fact that the reducing power of the manganese dioxide is so great that the cathodic potential is very negative and the acidity of the bath surrounding the cathode is low. It appears, therefore, that also for the cathode it is desirable to select a pH which is as high as possible but, however,

quite distant from the pH corresponding to the precipitation of the m'anganous hydroxide.

Accordingly, the invention provides a device by means" of which manganese dioxide may be manufactured by electrolysis, wherein the pH in the anodic region and the pH in the cathodic region may be separately best adjusted, so as to provide a suitable adherence of the manganese dioxide on the anode, and a good reduction of the impure manganese dioxide contained in the cathode.

The invention provides a device wherein the stability of the composition of the bath is maintained during th electrolysis process, so that said composition is constantly equal or close to the optimum composition.

The invention also provides a galvanic tank suitable for the preparation of manganese dioxide, which is characterized by the fact that it is subdivided into an anodic compartment and a cathodic compartment by at least one diaphragm, means being provided for drawing solution from the anodic compartment, which is fed to the cathodic compartment, and for bringing a fraction of the solution, drawn from the cathodic compartment, back into the anodic compartment.

The invention further provides an electrolytic device for preparing manganese dioxide, which operates with a small quantity of solution which is continuously regenerated, said device comprising a galvanic tank divided, by at least one porous diaphragm, into one anodic compartment and one cathodic compartment; means connecting the anodic compartment with the cathodic compartment and enabling the solution to pass from one com ing filtrate into the anodic compartment of said galvanic tank.

The invention also provides a galvanic tank which opcrates under a low electrode potential difference lower than or equal to 3.5 volts and, preferably, close to one volt.

In one embodiment of the invention, the electrodes are vertically arranged within the galvanic tank, and

means, such as a siphon, are provided for carrying the solution from the upper portion of the anodic compartment to the lower portion of the cathodic compartment.

and other means are provided for carrying the solution contained in the upper portion of the cathodic compartment to the lower portion of the anodic compartment.

In such a galvanic tank having vertical electrodes, the anode may comprise metal bands (for instance, made of lead or stainless steel covered with a thin layer of lead.

deposited by electrolysis), laid side by side on a common support, while the cathode may ,comprise a similar metal band, but of corrugated form In a modified form, the active portion ,of thelcathodes may comprise granulated native manganese dioxide which is reduced by thecurrent into manganese protoxide, then into manganous Mn++ ions, thus becoming the source of the manganese to be transformed into dioxide at the anode, while the anode comprises an agglomerate of pure manganese dioxide (for instance, electrolytic manganese dioxide) madefrom a thick paste formed with said pure dioxide and a syrup of manganese nitrate (said plate being strongly compressed within a mould, and, after being withdrawn from the mould and dried, heated up to a temperature in the vicinity of 180 C.).

A modified form of anode comprises a metal sheet or wire gauze which has been covered with a layer of manganese dioxide by dipping it, for instance,vin a syrup of manganese nitrate, then drying and calcinating the resulting covering in order to transform it into manganese dioxide.

In a modified form of our improved device, the galvanic tank comprises substantially horizontal electrodes, the anode being disposed above the cathode; the cathode comprises a granulated mass of native manganese dioxide, at least one electrically conducting perforated sheet, and a filtering cloth; means being provided for drawing solution from the lower portion of the tank (below the cathode) and for carrying it back, after regeneration and purification, to the upper portion of said tank (above the anode).

These and other objects and advantages of the invention will more fully appear from the following description, given by way of merely illustrating various embodiments suitable to carry it into practice, and taken in connection with the somewhat diagrammatical drawings in which:

Fig. 1 shows, in perspective view, a vertical crosssection of a first embodiment of our improved device according to the invention, with vertically disposed elec trodes;

Fig. 2 shows the anode of the device shown in Fig. 1, drawn at a larger scale;

Fig. 3 shows a modified form of said anode;

Fig. 4 shows the cathode of the device shown in Fig. 1, drawn at a larger scale;

Fig. 5 shows a modified form of said cathode; and

Fig. 6 is a cross-section of a second embodiment of our device, wherein the electrodes are substantially horizontal.

Our improved device as shown in Fig. l essentially comprises a galvanic tank 1 subdivided into an anodic compartment 2 and a cathodic compartment 3, by means of porous walls or partitions 4 constituted by a web made of superpolyamid, of asbestos or any equivalent material.

In the compartment 2 is an anode 5 (shown in Fig. 2 at a larger scale and described in a more detailed manner hereinafter) connected by a cable 6 to the positive terminal of a suitable D. C. source (not shown).

In the compartment 3 is a cathode 7 (shown in Fig. 4 at a larger scale, and described in greater detail hereinafter) made of an electrically conducting, corrosion resistant material, e. g. of lead, said cathode being connected, by a cable 8, to the negative terminal of the above mentioned D. C. source (not shown).

A siphon 9 provides for passing solution from the upper portion of the anodic compartment 2 to the lower portion of the cathodic compartment 3.

Up to a suitable level 10 (somewhat below the opening 11 of siohon 9), the tank 1 is fed with a suitable electrolyte 12, such as a solution of a manganese salt, e. g. a solution of manganese sulfate containing 25 gr. of manganese per liter and acidulated by gr. of sulfuric acid H 50 per liter.

When utilizing a tank such as 1 in Fig. 1, we have found that excellent results are obtained with a current density of one ampere per square decimeter, at the anode CPI cathode where they lose their charge to give either metallic manganese or (by a secondary reaction) hydrogen and manganous hydroxide Mn(OH) while, at the anode, the S0,;- ions lose their charge and produce nascent oxygen by secondary reaction (a fraction of this oxygen provides for the oxydation of the manganese sulfate, while the remainder is liberated as gas).

Owing to the utilization of diaphragms, such as 4, according to the invention, the pH may be separately adjusted to its optimum value, on the one hand, in the anodic compartment 2, and, on the other hand, in the cathodic compartment 3. This prevents the formation of a complex deposit on the cathode, which would present a high electrical resistance in the known producing methods, and the manufacturing operations may be performed with the reduced electrode potential difference (3 volts), as previously described.

As previously described, in the course of operation, the cathodic region has a tendency to become less and less acid, while the anodic region becomes more and more acid.

According to a feature of our invention, in order to maintain a practically constant acidity in each anodic and cathodic compartment during the electrolysis, a circulation is provided between the solutions respectively located within the anodic compartment 2 and cathodic compartment 3, for instance, in the following manner:

(1) The siphon 9 is such that its short branch 9a (ending into the opening 11) dips somewhat into the upper portion of electrolyte 12a within the compartment 2, while the long branch 9b dips into electrolyte 121; within the compartment 3 down to the vicinity of the bottom of said compartment;

(2) The tank comprises an overflow 13 so provided on the side of the cathodic compartment 3 that the electrolyte 12b Within said cathodic compartment 3 may flow into a vessel 14 at the lower portion of which is connected a pipe 15 which leads into a pump 16. Said pump, constructed of a corrosion resistant metal, such as 18% Cr-8% Ni steel, drives the solution from the vessel 14 through a pipe 17 into a filter-press 18, from which the filtered solution reaches the anodic compartment 2 through a pipe 19.

Provided that, during the electrolysis, the average acidity of the bath shows a tendency to increase due to the elimination of manganese as dioxide depositing on the anode, it is necessary to constantly bring the average acidity back to a constant value, by continuously adding a suitable quantity of an alkaline component containing manganese to the electrolyte solution. To this end, through a spout 20, is added a powdered manganese compound 21 (such as manganese carbonate or protoxide), such addition being controlled by a rotary distributor 22, and said spout 20 being fed by means of a spiral conveyor or Archimedean screw 23. A stirring device 24, driven into rotation by a motor 25, .provides for a thorough mixing of the powder 21, coming from the spout 20, with the solution within the vessel 14.

As above specified, said powder 21, coming from the spout 20, is utilized for neutralizing the aforesaid increase in acidity of the electrolyte and for maintaining the manganese content of the bath substantially constant.

Thus, with the aid of the siphon 9 and of the unit comprising the overflow 13, the vessel 14, the pipes 15, 17 and 19, and the pump 16, the pH of the solution in the anodic compartment 2 is maintained at a constant value, and the pH of the solution in the cathodic compartment 3 is also maintained at a constant value.

In a modified form of circulating system, the siphon 9 is deleted when the diaphragms 4 are sufiiciently permeable, so that the hydrostatic balance is suflicient to cause a circulation of electrolyte from the anodic region towards the cathodic region.

Some electrode arrangements particularly suited for being utilized with a tank, such as 1 in Fig.1, and shown in Figs. 2 to 5 are described hereinafter.

It is advantageous to utilize cathodes having a large surface and a small overall size, in order to be able to reduce the density of the cathodic current to a value lower than or equal to one ampere per square decimeter, and, consequently, to reduce the insulating deposit of manganous hydroxide on the cathode. With this end in view, each cathode 7 may comprise (as shown in Fig. 4) a metal sheet, of lead or other suitable electrically conducting material, forming corrugations, such as 26.

The anode 5, as shown in Fig. 2 at a larger scale, comprises several thin lead bands 5a, the thickness of which is, for instance, of about 2 mm. Such bands 5a are secured side by side (at a small distance from each other) by their upper end portion to a support 35 in the shape of a clamp, in order that they may be readily positioned and removed.

Since the electrolytic manganese dioxide deposited on the bands 5a is very brittle, the stripping of said deposit from said bands is easily performed by sufliciently bending the bands 5a, when they are covered with manganese dioxide, thereby easily breaking, peeling 03 or, in any other manner, separating such deposit from the anode. After having removed the manganese dioxide, each band 5a is straightened and planished without deteriorating it, in order to be able to insert it again into the support 35.

While remaining within the scope of our invention, the anode may comprise a plate or cylinder of electrolytic manganese dioxide (Fig. 3). To this end, a thick paste is prepared with electrolytic manganese dioxide, reduced in fine powder, and a syrup of manganese nitrate dissolved in water. Then said paste is strongly compressed into moulds. It is dried, and heated up to a temperature of 180 C., for causing the decomposition of the manganese nitrate into nitrous vapors and manganese dioxide, the latter providing a reinforcing element for the anodes thus produced and imparting them their mechanical strength.

For providing current input contact members for the anodes, before heating a plate or cylinder mass 27 of manganese dioxide to 180 C., as above described, a contact member, such as 28, in the form of a lead band or of a gas carbon plate, is being embedded into said mass 27.

When said input contact member 28 is made of lead, said contact member is not in direct contact with the bath, thereby largely avoiding an eventual corrosion effect leading to the formation of lead sulfate, which might pollute the collected dioxide.

When said input contact member 28 is made of gas carbon or graphite, the dioxide stripping operation is omitted and the anodes may merely be crushed with their carbon core. As a matter of fact, the depolarizing element in cells consists of a mixture of carbon and manganese dioxide, and this is the principal commercial use to which electrolytic manganese dioxide is put.

Similarly, the cathode may comprise a briquet or com pressed element made of native manganese dioxide (which may be mixed with carbon powder to impart a sufiicient electrical conductivity to it); said element may be advantageously stored in a sack or similar container.

For instance, as shown in Fig. 5, a cathode, such as 7", may be produced by utilizing a porous container or a bag made of filte'ring'cloth, such as'30, inside of which are placed a lead strip 31 electrically connected to a wire 6 and surrounded with granules 32 of native manganese dioxide, passing, for instance, the screen No. (corresponding to 20 meshes in a length of 27.77 mm.) in the French classification.

'In the cathodic region the electrolyte acts as a strong reducing agent; therefore, the native manganese dioxide is reduced and forms manganese sulfate which is diffused into the solution. In this manner, the composition of the electrolytic solution is maintained substantially constant and, accordingly, the quantity of powder, such as anode.

In Fig. 6 is shown an embodiment of our invention having horizontal electrodes, which is particularly suitable when utilizing a cathode containing oxygen compounds of manganese. The same reference numbers are used for designating similar or corresponding elements in Figs. 1 and 6, such numbers being provided with a prime in Fig. 6.

The improved device shown in Fig. 6 comprises a tank 1 subdivided ,into an anodic compartment 2 and a cathodic compartment 3', by a very porous diaphragm 4'. In the anodic compartment 2' are disposed anodes, such as 5 (the sole anode visible in Fig. 6), constituted by sheets of lead, while, in the cathodic compartment 3', is embedded a complex cathode 7 comprising:

A granulated mass of native manganese dioxide calibrated, for instance, with screen No. 20, as above described;

A perforated sheet 7b made of lead;

A filtering cloth 7c; and

A perforated sheet 7d made of lead.

The lead sheet 7b is electrically connected to the tank 1, which is made of an electrically conducting material. such as lead.

The anodes 5' (electrically insulated from the tank 1, by insulating blocks 33) are electrically connected to the positive terminal of a source of current (not shown) by a conducting cable 6, while, by a cable 8, the negative terminal of said source is electrically connected to the tank 1, which, as above mentioned, is in electrical contact with the sheet 7b of the cathode.

The anodic solution 12a may easily ditfuse through 'the diaphragm 4' of the' anodic compartment 2' into the cathodic compartment 3 to mix with the cathodic solution 12b.

Besides, at the lower portion of the tank 1' is provided a discharge pipe 34 carrying the cathodic solution 12b into a vessel 14 from which said solution is taken by a pipe 15 delivering it into a pump 16 which drives the cathodic solution back through a pipe 17, a filter-press 18 and a pipe 19, in order to bring said solution into the anodic compartment 2'.

As in the case of the embodiment of Fig. l, a powdered manganese compound 21 may be introduced into the vessel 14 through a spout 20 (the feeding device supplying powder 21 to the spout 20 is not shown in Fig. 6), a stirring device 24 mixing the powder and the acid solution which are contained within said vessel 14.

In the embodiment shown in Fig. 6, the cathode 7' comprises a granulated mass of native manganese dioxide, thus avoiding the expense of reducing the manganese dioxide Mn0 into manganese protoxide MnO, and re ducing the consumption of energy by lowering the electrode potential difierence, for instance, from 3 volts to one volt.

Furthermore, due to the presence of manganese dioxide at the cathode, there is no hydrogen evolution at the cathode, on account of the fact that the hydrogen produced by electrolytic decomposition is burnt by the manganese dioxide. Moreover, the cathode is depolarized by the same manganese dioxide. I

When utilizing a cathode such as 7' shown in Fig. 6, the manganese dioxide progressively disappears, and,

hours) it is necessary to refill the cathode .7"by adding a newdayer'of'native' dioxide to it.

In order that, those skilled inv the art may better understandhow our present'invention iscarried into effect, two illustrated examples are. given hereinafter:

Example 1 In adevice-of the-type as shown in: Fig. 1, i. e.. comprising agalvanic tank with ananodeconstituted by several'thin=lead'bands, such as' shown' in Fig. 2, and a cathode made of a corrugated sheet' of lead, such'as' shown in Fig. 4, is introduced a solution of manganese sulfate, containingZSfgr; manganese per' liter, and sulfuric acid, containing lgr. SO H per liter. During the electrolysis operation, the temperature'has been maintained at 70 C; and'a current-density of one ampere per. square decimeterhas been appliedatthe anode andiat' the cathode. For a gap" of 5" cm. between the electrodes, a potential difference of 3.5 volts is applied between the electrodes. 1,300 gr. of manganese dioxide have been produced per 1,000 ampere-hours, that is to say a consumption of energy per 1,000 gr. of manufactured MnO equal to:

=2,690 watt-hours, i. e. 2.69 kwh.

Example 2' Ina galvanic tank withhorizontal arrangement of the.

electrodes, such as shown in Fig. 6, the cathode comprising native manganese dioxide and the anode comprising a sheet of lead, the operation'has been conducted as follows.

A solution of manganese sulfate, containing 25 gr. manganese per literand gr. H 80 per liter, has been introduced into the tank. The operating temperature was 70 C. For an exposed surface of 1 square meter at the anode and at thecathode, a current intensity of 100 amperes has been applied, that is to say a current density of 1 ampere per square decimeter at the anode and at the cathode. tential difference to one volt; the. delivery. ofthe pump was 50 liters per hour.

Under such conditions, and a 24 houreoperation (after which it has been necessary to refill the electrode, on account of the dissolution of the native manganese di-, oxide), 1,400 gr. of manganese dioxide (particularly suited for the manufacture of dry cells) have been. produced per 1,000 ampere-hours, that is tosay a consumption of energy per 1,000 gr. of manufactured manganese dioxide equal to:

a consumption of energy which amounts but to about 25% of the consumption of energy found in the first example.

In order to neutralize the excessof acidity, .it has been necessary to add 82 gr. manganese protoxide MnO per 1,000 gr. of manufactured manganese dioxide MnO that is to say a quantity equal to aboutonetenth of the quantity added in the case of the first example.

While we have illustrated and described what we deem to be preferred embodiments of'our invention, it must be understood that various. changes and substitutions includingthe size, shape, number, and arrangements of parts, and the nature and'the. composition of utilized products, may be made withoutfdeparting frornthe spirit of our invention and itis notourintention to limit its scope other than by the terms of the appcnd f'd claims.

=710 Wattliours, i. e. 0.71 kwh It was possible to reduce thepo In the foregoing description as. wellas in the'appended.

claims, the words anode and cathode may justas wellj cover a single element or several ones. For instance, the anode may comprise severalialigned bands, as shown in Fig. 2, or several parallel vertical strips (the whole, unit constituting a horizontal anode), as in the embodiment shown in Fig, 6.

What we clairnis;v

, 1..A. device,for manufacturing, manganese. dioxide by electrolysis, comprisinga tank unitv adapted to receive an electrolyte constituted'by' a manganese salt and. subdivided,;by at,least.one.diaphragm,,into one anodic compartmentwith at least one. anode androne cathodic come partment.;wi th atpleast. one cathode located below said anodic compartment, each. cathode. comprisinga granulated. mass .of native. manganese dioxide. and. at? least one perforated electrically conducting sheet supporting. said masstof; manganese. dioxide; means for. withdrawing, electrolyte from. said cathodic. compartment andfor adding thereto a. manganese compound, and' means for thereafter. delivering saidjwithdrawn electrolyte into saidanodic compartment.

2. A. device. for manufacturingmanganese.dioxide by electrolysis, comprising, an. electrically conducting tank unit adapted. to receive. an electrolyte constituted. by a manganesesalt; at. least one diaphragm, subdividingsaid tank unitv intolone. anodic compartment with at least one anode. andone cathodic compartment'with at. least. one cathode; and located: below said. anodic: compartment, each. cathode,v comprising. a. granulated. mass of. native manganese dioxide, a. perforated electrically conducting sheet, a, filtering cloth member and. a: second. perforated.

sheetmember, in superposed disposition withsaidperforated. sheet members supporting said. mass of: man? ganesedioxide, and means .for. electrically connecting said perforated;conductingsheet with. said electrically con. ducting .tank unit; means for. withdrawing. electrolyte from said cathodic compartment and for adding thereto amanganese compound, and means for. thereafter. delivering saidlwithdrawnv electrolyte. into. said anodiccompartment.

3. A. device for manufacturing.manganese. dioxide by, electrolysis, comprising a tankzunit adapted to.receive an electrolyte of the type containing a manganese salt, said tank. being subdivided intov an anodic compartment providedwith at.least.one anode. and acathodic compartment:pIOVidd-,Withat least one cathode, each cathode comprising a. granulated mass ofnativemanganese dioxide, and means for maintainingga constant acidity in said,compartments, comprising :means through which said electrolyte is\ continuously transferred from'said. anodic compartmentto.said. cathodic compartment, means for withdrawing electrolyte-fromsaid cathode compartment andadding; thereto a manganese-compound and means for'thereafterjdelivering said withdrawn electrolyte into said anodiccornpartment.

4.. A-. de,vice according-to,claim,-3, .wherein the anodic and cathodic; compartments are disposed side by side and the electrodes are substantially: vertical.

A device accordinglto claim 4, whereinthe anode comprisesametal sheet member" covered. by. alayer of pure manganese' dioxide.

6.- A device-according to .-claim 4, wherein-the anode comprises a. metal sheet member. coveredby'a layer of purev manganese dioxide: obtained. by dipping: the. same into a;syrup of;manganese-nitr ate, vdry-ing-thesanie, and finally. calcinating it.

7. A- device according-to claim,4;wherein the anode is made of pure manganese dioxide. 7

8.. A: devicev according; to claim.- 4, wherein.) the; anode is m'ade. of: pure manganese dioxide obtained? from a thick paste, made of puremanganese;dioxidewancka syrupof nitrate o f manganese, strongly:compressediin a mould, withdrawn from said I mould; and finally;- heated up i to a temperature in the 'vicinity' of C;

9. A device according to claim 4, wherein the active portion of said cathode comprises native manganese dioxide.

10. A process for producing manganese dioxide in an electrolytic tank having separate anode and cathode compartments which process comprises the steps of introducing into said cathode compartment an electrolyte comprising a manganese salt, which electrolyte has the minimum acidity required to prevent precipitation of manganous hydroxide, and introducing into said anode compartment an electrolyte likewise comprising a manganese salt and having an acidity which results in the satisfactory adherence of the manganese dioxide formed to the anode, and maintaining a constant acidity in each compartment by continuously withdrawing electrolyte from said anode compartment and introducing it into said cathode compartment while simultaneously withdrawing electrolyte from said cathode compartment, increasing the alkalinity and manganese content thereof, and then introducing it into said anode compartment.

11. A process as claimed in claim 10 in which the acidity in said anode compartment is of the order of 2 to 3 grams of H 80, per liter.

12. A process as claimed in claim 11 in which a po tential difierence no greater than 3.5 volts is maintained between said anode and said cathode with a current density of one ampere per square decimeter.

13. A process as claimed in claim 10 in which said acidities are regulated in part by varying the volume of electrolyte transferred from each compartment to the other.

References Cited in the file of this patent UNITED STATES PATENTS 1,322,000 Ellis Nov. 18, 1919 1,878,244 Laury Sept. 20, 1932 2,011,171 Baker Aug. 13, 1935 2,340,254 Stewart Jan. 25, 1944 2,341,356 Briggs Feb. 8, 1944 2,424,958 Clemens Aug. 5, 1947 2,741,591 Dewey Apr. 10, 1956 FOREIGN PATENTS 14,988 Great Britain of 1896 

1. A DEVICE FOR MANUFACTURING MANGANESE DIOXIDE BY ELECTROLYSIS, COMPRISING A TANK UNIT ADAPTED TO RECEIVE AN ELECTROLYTE CONSTITUTED BY A MANGANESE SALT AND SUBDIVIDED, BY AT LEAST ONE DIAPHRAGM, INTO ONE ANODIC COMPARTMENT WITH AT LEAST ONE ANODE AND ONE CATHODIC COMPARTMENT WITH AT LEAST ONE CATHODE LOCATED BELOW SAID ANODIC COMPARTMENT, EACH CATHODE COMPRISING A GRANULATED MASS OF NATIVE MANGANESE DIOXIDE AND AT LEAST ONE PERFORATED ELECTRICALLY CONDUCTING SHEET SUPPORTING SAID MASS OF MANGANESE DIOXIDE; MEANS FOR WITHDRAWING ELECTROLYTE FROM SAID CATHODIC COMPARTMENT AND FOR ADDING THERETO A MANGANESE COMPOUND, AND MEANS FOR THEREAFTER DELIVERING SAID WITHDRAWN ELECTROLYTE INTO SAID ANODIC COMPARTMENT. 